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Warm white refers to some particular average. But how do you find led’s that don’t hide a spike of blue light in that average? Most places where I run into led-
by CuriousSkeptic 7y ago
Warm white refers to some particular average. But how do you find led’s that don’t hide a spike of blue light in that average? Most places where I run into led-lights don’t advertise the spectral distribution.
- hoytech 7y agoThis is a really fun and easy experiment you might like: https://www.cs.cmu.edu/~zhuxj/astro/html/spectrometer.html https://www.cs.cmu.edu/~zhuxj/astro/html/spectrometer.html
- marak830 7y agoOh that's awesome! I have a colleague writing a semester on science projects for kids, this is definitely going to fit in with that!
- peatmoss 7y agoMy understanding is that LEDs have a very specific, peaky distribution. Heating a wire results in a wide distribution of color temps, but solid state lighting is a really narrow band of color. I have a photo panel that needs two separate color LEDs to produce a balanced feeling color temp.
- _ph_ 7y agoAs I wrote (https://news.ycombinator.com/item?id=19919819 https://news.ycombinator.com/item?id=19919819) LEDs usually have a single color: blue. However the resulting spectrum generated by the phosphor can have almost any shape, some high-quality LEDs even have a pretty perfect black body spectrum without a blue line. Of course they are more expensive and also less efficient.
- danharaj 7y ago> some high-quality LEDs Where can I get these?
- jarvist 7y agoIn terms of commercially available bulbs, the 'Philips Master LED ExpertColor' (all in spotlight 'GU10' etc. format) have an extremely high quality halogen-like spectrum.
- _ph_ 7y agoSearch for "high CRI LEDs". This should turn up LED module vendors which usually have the data sheets which should include a LED spectrum. The warmer the LED temperature is, the smaller the blue peak. For example here: https://www.led1.de/shop/files/Datenblaetter/Osram-OS/Oslon/GW_CSSRM1_BM_-_OSLON_SQUARE_CRI_95__EnglishDeutsch_.pdf https://www.led1.de/shop/files/Datenblaetter/Osram-OS/Oslon/... or here https://lumstatic.com/9p/Vt/uRNvyjbnQnfzzgO6rg.pdf https://lumstatic.com/9p/Vt/uRNvyjbnQnfzzgO6rg.pdf.
- Paianni 7y agoSoraa.
- _ph_ 7y agoI really hope, someone makes a cheap spectrometer as a smartphone accessory. That would be the best way to quickly assess the properties of light sources. Beyond the health impact, one wants to know the light spectrum when e.g. selecting lamps for fish tanks or plant lighting. As a very coarse but easily available poor-mans spectrometer, I have been taking pictures of a greycard with my camera in raw-mode. Looking at the histogram balanced for a fixed color temperature, e.g. sunlight, for the r,g,b-channels gives very different results depending on different light sources. While you don't see a true spectrum, just the strength of the blue vs. the green and red channel usually is very revealing.
- scotty79 7y agoIt's cheap and works without the smartphone https://www.ebay.com/sch/i.html?_odkw=Diffraction+&_from=R40&_trksid=m4084.l1313&_nkw=Diffraction+grating+slides https://www.ebay.com/sch/i.html?_odkw=Diffraction+&_from=R40...
- _ph_ 7y agoYes, that is a good start - I would like to have curve with the relative strengths of the spectrum. But maybe it is enough to carefully calibrate the smartphone camera on the diffraction sprectra to generate a course graph. Also, if no diffraction grating is at hand, a random audio CD usually is up to the task :)
- gtrubetskoy 7y agoAny compact disk works as a spectrometer. https://www.cs.cmu.edu/~zhuxj/astro/html/spectrometer.html https://www.cs.cmu.edu/~zhuxj/astro/html/spectrometer.html
- NIL8 7y agoI've never seen this. Thanks!
- janekm 7y agoThat only shows differences in white balance and tone. It can't give you any information about the CRI since you only have 3 channels of colour sensors in your camera. If you use a colour swatch palette that would be different.
- scotty79 7y agoSee for yourself: https://www.ebay.com/sch/i.html?_odkw=Diffraction+&_from=R40&_trksid=m4084.l1313&_nkw=Diffraction+grating+slides https://www.ebay.com/sch/i.html?_odkw=Diffraction+&_from=R40...
- Someone1234 7y agoI was skeptical, but great link. I might order one to play with. I didn't even realize that was a thing.
- oasisbob 7y agoCRI is a common metric for LED lighting. I'm not intimately familiar with the standard, but would expect a large spectral aberration to negatively impact the CRI. When I was building up some high-CRI architectural fixtures, finding fully characterized LEDs wasn't much of an issue. At the consumer level it can be tough to get good details beyond color temperature.
- jwr 7y agoI am designing my own lighting and I found the same thing. There is a huge discrepancy between what you can get at the source from manufacturers and what ends up in "consumer" hands. Most of what is sold in the stores is poorly-specified crap, built to be as cheap as possible.
- mindslight 7y agoJust guessing from what I know about LEDs and efficiency, I suspect they all just hide a spike of the same blue light in that average.